In recent years, augmented reality (AR) technology of synthesizing and presenting a virtual object as additional information or various types of information as electronic information to a real environment (or a portion thereof) has attracted much attention. In order to implement the augmented reality technology, as an apparatus presenting visual information, for example, a head mounted display has been studied. In addition, as an application field, work supporting in the real environment is expected. For example, providing of road guidance information, providing of technical information to technicians who perform maintenance or the like may be exemplified. Particularly, since there is no possibility that the hands are not blocked, the head mounted display is very convenient. In addition, even in case of intending to enjoy a video or an image while moving outdoors, since the video or image and an external environment can be simultaneously recognized within eyesight, smooth movement can be performed.
A virtual image display apparatus (display apparatus) for allowing a virtual image optical system to enable an observer to observe a two-dimensional image formed by an image forming device as an enlarged virtual image is well known from, for example, Japanese Patent Application Laid-Open No. 2006-162767.
As illustrated in a conceptual diagram of FIG. 26, the image display device 100′ is configured to include an image forming device 111 having a plurality of pixels which are arrayed in a two-dimensional matrix shape, a collimating optical system 112 converting light emitted from the pixels of the image forming device 111 to parallel light, and an optical device 120 which light converted to the parallel light in the collimating optical system 112 is incident on and which guides and emits the light. The optical device 120 is configured to include a light guiding plate 121 which propagates the incident light through the inner portion thereof by total reflection and emits the light, a first deflecting unit 130 (configured with, for example, a single-layered light reflecting film) which reflects the light incident on the light guiding plate 121 so that the light incident on the light guiding plate 121 is totally reflected through the inner portion of the light guiding plate 121, and a second deflecting unit 140 (configured with, for example, a multi-layered light reflecting film having a multi-layer stacked structure) which emits the light propagating through the inner portion of the light guiding plate 121 by total reflection from the light guiding plate 121. In addition, for example, if an HMD is configured by using such an image display device 100′, a light-weighted, small-sized apparatus can be implemented. In addition, with respect to reference numerals indicating other components in FIG. 26, the image display device of Example 1 described with reference to FIG. 5 is referred to.
Alternatively, a virtual image display apparatus (display apparatus) using a hologram diffraction grating for allowing a virtual image optical system to enable an observer to observe a two-dimensional image formed by an image forming device as an enlarged virtual image is well known from, for example, Japanese Patent Application Laid-Open No. 2007-094175.
As illustrated in a conceptual diagram of FIG. 27, the image display device 300′ is basically configured to include an image forming device 111 displaying an image, a collimating optical system 112, and an optical device 320 which light displayed in the image forming device 111 is incident on and which guides the light to observer's pupils 21. Herein, the optical device 320 is configured to include a light guiding plate 321 and a first diffraction grating member 330 and a second diffraction grating member 340 which are configured with reflection type volume hologram diffraction gratings provided to the light guiding plate 321. In addition, light emitted from each pixel of the image forming device 111 is incident on the collimating optical system 112, and a plurality of parallel light beams having difference incident angles with respect to the light guiding plate 321 are generated by the collimating optical system 112 and are incident on the light guiding plate 321. The parallel light is incident from the first plane 322 of the light guiding plate 321 and is emitted. On the other hand, the first diffraction grating member 330 and the second diffraction grating member 340 are attached to the second plane 323 of the light guiding plate 321 which is parallel to the first plane 322 of the light guiding plate 321. In addition, with respect to reference numerals indicating other components in FIG. 27, the image display device of Example 5 described with reference to FIG. 16 is referred to.
In addition, a virtual image based on the image is formed in the image display device 100′, 300′, so that the observer can view an image of an outside world and the formed virtual image in an overlapped manner.
However, in the case of a peripheral environment where the image display device 100′, 300′ is located is very bright or according to a content of the formed virtual image, there is a problem in that sufficient contrast is not exhibited in the virtual image observed by the observer. In addition, means for solving the problems, that is, a virtual image display apparatus (display apparatus) having a dimming device are well known from, for example, Japanese Patent Application Laid-Open No. 2012-252091.